// dear imgui: Renderer Backend for modern OpenGL with shaders / programmatic pipeline
// - Desktop GL: 2.x 3.x 4.x
// - Embedded GL: ES 2.0 (WebGL 1.0), ES 3.0 (WebGL 2.0)
// This needs to be used along with a Platform Backend (e.g. GLFW, SDL, Win32, custom..)

// Implemented features:
//  [X] Renderer: User texture binding. Use 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID!
//  [X] Renderer: Multi-viewport support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
//  [x] Renderer: Desktop GL only: Support for large meshes (64k+ vertices) with 16-bit indices.

// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
// Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
// If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
// Read online: https://github.com/ocornut/imgui/tree/master/docs

// CHANGELOG
// (minor and older changes stripped away, please see git history for details)
//  2022-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
//  2021-12-15: OpenGL: Using buffer orphaning + glBufferSubData(), seems to fix leaks with multi-viewports with some Intel HD drivers.
//  2021-08-23: OpenGL: Fixed ES 3.0 shader ("#version 300 es") use normal precision floats to avoid wobbly rendering at HD resolutions.
//  2021-08-19: OpenGL: Embed and use our own minimal GL loader (imgui_impl_opengl3_loader.h), removing requirement and support for third-party loader.
//  2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
//  2021-06-25: OpenGL: Use OES_vertex_array extension on Emscripten + backup/restore current state.
//  2021-06-21: OpenGL: Destroy individual vertex/fragment shader objects right after they are linked into the main shader.
//  2021-05-24: OpenGL: Access GL_CLIP_ORIGIN when "GL_ARB_clip_control" extension is detected, inside of just OpenGL 4.5 version.
//  2021-05-19: OpenGL: Replaced direct access to ImDrawCmd::TextureId with a call to ImDrawCmd::GetTexID(). (will become a requirement)
//  2021-04-06: OpenGL: Don't try to read GL_CLIP_ORIGIN unless we're OpenGL 4.5 or greater.
//  2021-02-18: OpenGL: Change blending equation to preserve alpha in output buffer.
//  2021-01-03: OpenGL: Backup, setup and restore GL_STENCIL_TEST state.
//  2020-10-23: OpenGL: Backup, setup and restore GL_PRIMITIVE_RESTART state.
//  2020-10-15: OpenGL: Use glGetString(GL_VERSION) instead of glGetIntegerv(GL_MAJOR_VERSION, ...) when the later returns zero (e.g. Desktop GL 2.x)
//  2020-09-17: OpenGL: Fix to avoid compiling/calling glBindSampler() on ES or pre 3.3 context which have the defines set by a loader.
//  2020-07-10: OpenGL: Added support for glad2 OpenGL loader.
//  2020-05-08: OpenGL: Made default GLSL version 150 (instead of 130) on OSX.
//  2020-04-21: OpenGL: Fixed handling of glClipControl(GL_UPPER_LEFT) by inverting projection matrix.
//  2020-04-12: OpenGL: Fixed context version check mistakenly testing for 4.0+ instead of 3.2+ to enable ImGuiBackendFlags_RendererHasVtxOffset.
//  2020-03-24: OpenGL: Added support for glbinding 2.x OpenGL loader.
//  2020-01-07: OpenGL: Added support for glbinding 3.x OpenGL loader.
//  2019-10-25: OpenGL: Using a combination of GL define and runtime GL version to decide whether to use glDrawElementsBaseVertex(). Fix building with pre-3.2 GL loaders.
//  2019-09-22: OpenGL: Detect default GL loader using __has_include compiler facility.
//  2019-09-16: OpenGL: Tweak initialization code to allow application calling ImGui_ImplOpenGL3_CreateFontsTexture() before the first NewFrame() call.
//  2019-05-29: OpenGL: Desktop GL only: Added support for large mesh (64K+ vertices), enable ImGuiBackendFlags_RendererHasVtxOffset flag.
//  2019-04-30: OpenGL: Added support for special ImDrawCallback_ResetRenderState callback to reset render state.
//  2019-03-29: OpenGL: Not calling glBindBuffer more than necessary in the render loop.
//  2019-03-15: OpenGL: Added a GL call + comments in ImGui_ImplOpenGL3_Init() to detect uninitialized GL function loaders early.
//  2019-03-03: OpenGL: Fix support for ES 2.0 (WebGL 1.0).
//  2019-02-20: OpenGL: Fix for OSX not supporting OpenGL 4.5, we don't try to read GL_CLIP_ORIGIN even if defined by the headers/loader.
//  2019-02-11: OpenGL: Projecting clipping rectangles correctly using draw_data->FramebufferScale to allow multi-viewports for retina display.
//  2019-02-01: OpenGL: Using GLSL 410 shaders for any version over 410 (e.g. 430, 450).
//  2018-11-30: Misc: Setting up io.BackendRendererName so it can be displayed in the About Window.
//  2018-11-13: OpenGL: Support for GL 4.5's glClipControl(GL_UPPER_LEFT) / GL_CLIP_ORIGIN.
//  2018-08-29: OpenGL: Added support for more OpenGL loaders: glew and glad, with comments indicative that any loader can be used.
//  2018-08-09: OpenGL: Default to OpenGL ES 3 on iOS and Android. GLSL version default to "#version 300 ES".
//  2018-07-30: OpenGL: Support for GLSL 300 ES and 410 core. Fixes for Emscripten compilation.
//  2018-07-10: OpenGL: Support for more GLSL versions (based on the GLSL version string). Added error output when shaders fail to compile/link.
//  2018-06-08: Misc: Extracted imgui_impl_opengl3.cpp/.h away from the old combined GLFW/SDL+OpenGL3 examples.
//  2018-06-08: OpenGL: Use draw_data->DisplayPos and draw_data->DisplaySize to setup projection matrix and clipping rectangle.
//  2018-05-25: OpenGL: Removed unnecessary backup/restore of GL_ELEMENT_ARRAY_BUFFER_BINDING since this is part of the VAO state.
//  2018-05-14: OpenGL: Making the call to glBindSampler() optional so 3.2 context won't fail if the function is a NULL pointer.
//  2018-03-06: OpenGL: Added const char* glsl_version parameter to ImGui_ImplOpenGL3_Init() so user can override the GLSL version e.g. "#version 150".
//  2018-02-23: OpenGL: Create the VAO in the render function so the setup can more easily be used with multiple shared GL context.
//  2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplSdlGL3_RenderDrawData() in the .h file so you can call it yourself.
//  2018-01-07: OpenGL: Changed GLSL shader version from 330 to 150.
//  2017-09-01: OpenGL: Save and restore current bound sampler. Save and restore current polygon mode.
//  2017-05-01: OpenGL: Fixed save and restore of current blend func state.
//  2017-05-01: OpenGL: Fixed save and restore of current GL_ACTIVE_TEXTURE.
//  2016-09-05: OpenGL: Fixed save and restore of current scissor rectangle.
//  2016-07-29: OpenGL: Explicitly setting GL_UNPACK_ROW_LENGTH to reduce issues because SDL changes it. (#752)

//----------------------------------------
// OpenGL    GLSL      GLSL
// version   version   string
//----------------------------------------
//  2.0       110       "#version 110"
//  2.1       120       "#version 120"
//  3.0       130       "#version 130"
//  3.1       140       "#version 140"
//  3.2       150       "#version 150"
//  3.3       330       "#version 330 core"
//  4.0       400       "#version 400 core"
//  4.1       410       "#version 410 core"
//  4.2       420       "#version 410 core"
//  4.3       430       "#version 430 core"
//  ES 2.0    100       "#version 100"      = WebGL 1.0
//  ES 3.0    300       "#version 300 es"   = WebGL 2.0
//----------------------------------------

#if defined(_MSC_VER) && !defined(_CRT_SECURE_NO_WARNINGS)
#define _CRT_SECURE_NO_WARNINGS
#endif

#include "imgui.h"
#include "imgui_impl_opengl3.h"
#include <stdio.h>
#if defined(_MSC_VER) && _MSC_VER <= 1500 // MSVC 2008 or earlier
#include <stddef.h>     // intptr_t
#else
#include <stdint.h>     // intptr_t
#endif

// Clang warnings with -Weverything
#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wold-style-cast"     // warning: use of old-style cast
#pragma clang diagnostic ignored "-Wsign-conversion"    // warning: implicit conversion changes signedness
#if __has_warning("-Wzero-as-null-pointer-constant")
#pragma clang diagnostic ignored "-Wzero-as-null-pointer-constant"
#endif
#endif

// GL includes
#if defined(IMGUI_IMPL_OPENGL_ES2)
#if (defined(__APPLE__) && (TARGET_OS_IOS || TARGET_OS_TV))
#include <OpenGLES/ES2/gl.h>    // Use GL ES 2
#else
#include <GLES2/gl2.h>          // Use GL ES 2
#endif
#if defined(__EMSCRIPTEN__)
#ifndef GL_GLEXT_PROTOTYPES
#define GL_GLEXT_PROTOTYPES
#endif
#include <GLES2/gl2ext.h>
#endif
#elif defined(IMGUI_IMPL_OPENGL_ES3)
#if defined(__APPLE__)
#include <TargetConditionals.h>
#endif
#if (defined(__APPLE__) && (TARGET_OS_IOS || TARGET_OS_TV))
#include <OpenGLES/ES3/gl.h>    // Use GL ES 3
#else
#include <GLES3/gl3.h>          // Use GL ES 3
#endif
#elif !defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
// Modern desktop OpenGL doesn't have a standard portable header file to load OpenGL function pointers.
// Helper libraries are often used for this purpose! Here we are using our own minimal custom loader based on gl3w.
// In the rest of your app/engine, you can use another loader of your choice (gl3w, glew, glad, glbinding, glext, glLoadGen, etc.).
// If you happen to be developing a new feature for this backend (imgui_impl_opengl3.cpp):
// - You may need to regenerate imgui_impl_opengl3_loader.h to add new symbols. See https://github.com/dearimgui/gl3w_stripped
// - You can temporarily use an unstripped version. See https://github.com/dearimgui/gl3w_stripped/releases
// Changes to this backend using new APIs should be accompanied by a regenerated stripped loader version.
#define IMGL3W_IMPL
#include "imgui_impl_opengl3_loader.h"
#endif

// Vertex arrays are not supported on ES2/WebGL1 unless Emscripten which uses an extension
#ifndef IMGUI_IMPL_OPENGL_ES2
#define IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
#elif defined(__EMSCRIPTEN__)
#define IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
#define glBindVertexArray       glBindVertexArrayOES
#define glGenVertexArrays       glGenVertexArraysOES
#define glDeleteVertexArrays    glDeleteVertexArraysOES
#define GL_VERTEX_ARRAY_BINDING GL_VERTEX_ARRAY_BINDING_OES
#endif

// Desktop GL 2.0+ has glPolygonMode() which GL ES and WebGL don't have.
#ifdef GL_POLYGON_MODE
#define IMGUI_IMPL_HAS_POLYGON_MODE
#endif

// Desktop GL 3.2+ has glDrawElementsBaseVertex() which GL ES and WebGL don't have.
#if !defined(IMGUI_IMPL_OPENGL_ES2) && !defined(IMGUI_IMPL_OPENGL_ES3) && defined(GL_VERSION_3_2)
#define IMGUI_IMPL_OPENGL_MAY_HAVE_VTX_OFFSET
#endif

// Desktop GL 3.3+ has glBindSampler()
#if !defined(IMGUI_IMPL_OPENGL_ES2) && !defined(IMGUI_IMPL_OPENGL_ES3) && defined(GL_VERSION_3_3)
#define IMGUI_IMPL_OPENGL_MAY_HAVE_BIND_SAMPLER
#endif

// Desktop GL 3.1+ has GL_PRIMITIVE_RESTART state
#if !defined(IMGUI_IMPL_OPENGL_ES2) && !defined(IMGUI_IMPL_OPENGL_ES3) && defined(GL_VERSION_3_1)
#define IMGUI_IMPL_OPENGL_MAY_HAVE_PRIMITIVE_RESTART
#endif

// Desktop GL use extension detection
#if !defined(IMGUI_IMPL_OPENGL_ES2) && !defined(IMGUI_IMPL_OPENGL_ES3)
#define IMGUI_IMPL_OPENGL_MAY_HAVE_EXTENSIONS
#endif

// OpenGL Data
struct ImGui_ImplOpenGL3_Data
{
	GLuint          GlVersion;               // Extracted at runtime using GL_MAJOR_VERSION, GL_MINOR_VERSION queries (e.g. 320 for GL 3.2)
	char            GlslVersionString[32];   // Specified by user or detected based on compile time GL settings.
	GLuint          FontTexture;
	GLuint          ShaderHandle;
	GLint           AttribLocationTex;       // Uniforms location
	GLint           AttribLocationProjMtx;
	GLuint          AttribLocationVtxPos;    // Vertex attributes location
	GLuint          AttribLocationVtxUV;
	GLuint          AttribLocationVtxColor;
	unsigned int    VboHandle, ElementsHandle;
	GLsizeiptr      VertexBufferSize;
	GLsizeiptr      IndexBufferSize;
	bool            HasClipOrigin;

	ImGui_ImplOpenGL3_Data() { memset((void*)this, 0, sizeof(*this)); }
};

// Backend data stored in io.BackendRendererUserData to allow support for multiple Dear ImGui contexts
// It is STRONGLY preferred that you use docking branch with multi-viewports (== single Dear ImGui context + multiple windows) instead of multiple Dear ImGui contexts.
static ImGui_ImplOpenGL3_Data* ImGui_ImplOpenGL3_GetBackendData()
{
	return ImGui::GetCurrentContext() ? (ImGui_ImplOpenGL3_Data*)ImGui::GetIO().BackendRendererUserData : NULL;
}

// Forward Declarations
static void ImGui_ImplOpenGL3_InitPlatformInterface();
static void ImGui_ImplOpenGL3_ShutdownPlatformInterface();

// Functions
bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
{
	ImGuiIO& io = ImGui::GetIO();
	IM_ASSERT(io.BackendRendererUserData == NULL && "Already initialized a renderer backend!");

	// Initialize our loader
#if !defined(IMGUI_IMPL_OPENGL_ES2) && !defined(IMGUI_IMPL_OPENGL_ES3) && !defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
	if (imgl3wInit() != 0)
	{
		fprintf(stderr, "Failed to initialize OpenGL loader!\n");
		return false;
	}
#endif

	// Setup backend capabilities flags
	ImGui_ImplOpenGL3_Data* bd = IM_NEW(ImGui_ImplOpenGL3_Data)();
	io.BackendRendererUserData = (void*)bd;
	io.BackendRendererName = "imgui_impl_opengl3";

	// Query for GL version (e.g. 320 for GL 3.2)
#if !defined(IMGUI_IMPL_OPENGL_ES2)
	GLint major = 0;
	GLint minor = 0;
	glGetIntegerv(GL_MAJOR_VERSION, &major);
	glGetIntegerv(GL_MINOR_VERSION, &minor);
	if (major == 0 && minor == 0)
	{
		// Query GL_VERSION in desktop GL 2.x, the string will start with "<major>.<minor>"
		const char* gl_version = (const char*)glGetString(GL_VERSION);
		sscanf(gl_version, "%d.%d", &major, &minor);
	}
	bd->GlVersion = (GLuint)(major * 100 + minor * 10);
#else
	bd->GlVersion = 200; // GLES 2
#endif

#ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_VTX_OFFSET
	if (bd->GlVersion >= 320)
		io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
#endif
	io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports;  // We can create multi-viewports on the Renderer side (optional)

	// Store GLSL version string so we can refer to it later in case we recreate shaders.
	// Note: GLSL version is NOT the same as GL version. Leave this to NULL if unsure.
	if (glsl_version == NULL)
	{
#if defined(IMGUI_IMPL_OPENGL_ES2)
		glsl_version = "#version 100";
#elif defined(IMGUI_IMPL_OPENGL_ES3)
		glsl_version = "#version 300 es";
#elif defined(__APPLE__)
		glsl_version = "#version 150";
#else
		glsl_version = "#version 130";
#endif
	}
	IM_ASSERT((int)strlen(glsl_version) + 2 < IM_ARRAYSIZE(bd->GlslVersionString));
	strcpy(bd->GlslVersionString, glsl_version);
	strcat(bd->GlslVersionString, "\n");

	// Make an arbitrary GL call (we don't actually need the result)
	// IF YOU GET A CRASH HERE: it probably means the OpenGL function loader didn't do its job. Let us know!
	GLint current_texture;
	glGetIntegerv(GL_TEXTURE_BINDING_2D, &current_texture);

	// Detect extensions we support
	bd->HasClipOrigin = (bd->GlVersion >= 450);
#ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_EXTENSIONS
	GLint num_extensions = 0;
	glGetIntegerv(GL_NUM_EXTENSIONS, &num_extensions);
	for (GLint i = 0; i < num_extensions; i++)
	{
		const char* extension = (const char*)glGetStringi(GL_EXTENSIONS, i);
		if (extension != NULL && strcmp(extension, "GL_ARB_clip_control") == 0)
			bd->HasClipOrigin = true;
	}
#endif

	if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
		ImGui_ImplOpenGL3_InitPlatformInterface();

	return true;
}

void    ImGui_ImplOpenGL3_Shutdown()
{
	ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();
	IM_ASSERT(bd != NULL && "No renderer backend to shutdown, or already shutdown?");
	ImGuiIO& io = ImGui::GetIO();

	ImGui_ImplOpenGL3_ShutdownPlatformInterface();
	ImGui_ImplOpenGL3_DestroyDeviceObjects();
	io.BackendRendererName = NULL;
	io.BackendRendererUserData = NULL;
	IM_DELETE(bd);
}

void    ImGui_ImplOpenGL3_NewFrame()
{
	ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();
	IM_ASSERT(bd != NULL && "Did you call ImGui_ImplOpenGL3_Init()?");

	if (!bd->ShaderHandle)
		ImGui_ImplOpenGL3_CreateDeviceObjects();
}

static void ImGui_ImplOpenGL3_SetupRenderState(ImDrawData* draw_data, int fb_width, int fb_height, GLuint vertex_array_object)
{
	ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();

	// Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, polygon fill
	glEnable(GL_BLEND);
	glBlendEquation(GL_FUNC_ADD);
	glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
	glDisable(GL_CULL_FACE);
	glDisable(GL_DEPTH_TEST);
	glDisable(GL_STENCIL_TEST);
	glEnable(GL_SCISSOR_TEST);
#ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_PRIMITIVE_RESTART
	if (bd->GlVersion >= 310)
		glDisable(GL_PRIMITIVE_RESTART);
#endif
#ifdef IMGUI_IMPL_HAS_POLYGON_MODE
	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
#endif

	// Support for GL 4.5 rarely used glClipControl(GL_UPPER_LEFT)
#if defined(GL_CLIP_ORIGIN)
	bool clip_origin_lower_left = true;
	if (bd->HasClipOrigin)
	{
		GLenum current_clip_origin = 0; glGetIntegerv(GL_CLIP_ORIGIN, (GLint*)&current_clip_origin);
		if (current_clip_origin == GL_UPPER_LEFT)
			clip_origin_lower_left = false;
	}
#endif

	// Setup viewport, orthographic projection matrix
	// Our visible imgui space lies from draw_data->DisplayPos (top left) to draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayPos is (0,0) for single viewport apps.
	glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
	float L = draw_data->DisplayPos.x;
	float R = draw_data->DisplayPos.x + draw_data->DisplaySize.x;
	float T = draw_data->DisplayPos.y;
	float B = draw_data->DisplayPos.y + draw_data->DisplaySize.y;
#if defined(GL_CLIP_ORIGIN)
	if (!clip_origin_lower_left) { float tmp = T; T = B; B = tmp; } // Swap top and bottom if origin is upper left
#endif
	const float ortho_projection[4][4] =
	{
		{ 2.0f / (R - L),   0.0f,         0.0f,   0.0f },
		{ 0.0f,         2.0f / (T - B),   0.0f,   0.0f },
		{ 0.0f,         0.0f,        -1.0f,   0.0f },
		{ (R + L) / (L - R),  (T + B) / (B - T),  0.0f,   1.0f },
	};
	glUseProgram(bd->ShaderHandle);
	glUniform1i(bd->AttribLocationTex, 0);
	glUniformMatrix4fv(bd->AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0]);

#ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_BIND_SAMPLER
	if (bd->GlVersion >= 330)
		glBindSampler(0, 0); // We use combined texture/sampler state. Applications using GL 3.3 may set that otherwise.
#endif

	(void)vertex_array_object;
#ifdef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
	glBindVertexArray(vertex_array_object);
#endif

	// Bind vertex/index buffers and setup attributes for ImDrawVert
	glBindBuffer(GL_ARRAY_BUFFER, bd->VboHandle);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bd->ElementsHandle);
	glEnableVertexAttribArray(bd->AttribLocationVtxPos);
	glEnableVertexAttribArray(bd->AttribLocationVtxUV);
	glEnableVertexAttribArray(bd->AttribLocationVtxColor);
	glVertexAttribPointer(bd->AttribLocationVtxPos, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, pos));
	glVertexAttribPointer(bd->AttribLocationVtxUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, uv));
	glVertexAttribPointer(bd->AttribLocationVtxColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, col));
}

// OpenGL3 Render function.
// Note that this implementation is little overcomplicated because we are saving/setting up/restoring every OpenGL state explicitly.
// This is in order to be able to run within an OpenGL engine that doesn't do so.
void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
{
	// Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
	int fb_width = (int)(draw_data->DisplaySize.x * draw_data->FramebufferScale.x);
	int fb_height = (int)(draw_data->DisplaySize.y * draw_data->FramebufferScale.y);
	if (fb_width <= 0 || fb_height <= 0)
		return;

	ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();

	// Backup GL state
	GLenum last_active_texture; glGetIntegerv(GL_ACTIVE_TEXTURE, (GLint*)&last_active_texture);
	glActiveTexture(GL_TEXTURE0);
	GLuint last_program; glGetIntegerv(GL_CURRENT_PROGRAM, (GLint*)&last_program);
	GLuint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, (GLint*)&last_texture);
#ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_BIND_SAMPLER
	GLuint last_sampler; if (bd->GlVersion >= 330) { glGetIntegerv(GL_SAMPLER_BINDING, (GLint*)&last_sampler); }
	else { last_sampler = 0; }
#endif
	GLuint last_array_buffer; glGetIntegerv(GL_ARRAY_BUFFER_BINDING, (GLint*)&last_array_buffer);
#ifdef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
	GLuint last_vertex_array_object; glGetIntegerv(GL_VERTEX_ARRAY_BINDING, (GLint*)&last_vertex_array_object);
#endif
#ifdef IMGUI_IMPL_HAS_POLYGON_MODE
	GLint last_polygon_mode[2]; glGetIntegerv(GL_POLYGON_MODE, last_polygon_mode);
#endif
	GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
	GLint last_scissor_box[4]; glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
	GLenum last_blend_src_rgb; glGetIntegerv(GL_BLEND_SRC_RGB, (GLint*)&last_blend_src_rgb);
	GLenum last_blend_dst_rgb; glGetIntegerv(GL_BLEND_DST_RGB, (GLint*)&last_blend_dst_rgb);
	GLenum last_blend_src_alpha; glGetIntegerv(GL_BLEND_SRC_ALPHA, (GLint*)&last_blend_src_alpha);
	GLenum last_blend_dst_alpha; glGetIntegerv(GL_BLEND_DST_ALPHA, (GLint*)&last_blend_dst_alpha);
	GLenum last_blend_equation_rgb; glGetIntegerv(GL_BLEND_EQUATION_RGB, (GLint*)&last_blend_equation_rgb);
	GLenum last_blend_equation_alpha; glGetIntegerv(GL_BLEND_EQUATION_ALPHA, (GLint*)&last_blend_equation_alpha);
	GLboolean last_enable_blend = glIsEnabled(GL_BLEND);
	GLboolean last_enable_cull_face = glIsEnabled(GL_CULL_FACE);
	GLboolean last_enable_depth_test = glIsEnabled(GL_DEPTH_TEST);
	GLboolean last_enable_stencil_test = glIsEnabled(GL_STENCIL_TEST);
	GLboolean last_enable_scissor_test = glIsEnabled(GL_SCISSOR_TEST);
#ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_PRIMITIVE_RESTART
	GLboolean last_enable_primitive_restart = (bd->GlVersion >= 310) ? glIsEnabled(GL_PRIMITIVE_RESTART) : GL_FALSE;
#endif

	// Setup desired GL state
	// Recreate the VAO every time (this is to easily allow multiple GL contexts to be rendered to. VAO are not shared among GL contexts)
	// The renderer would actually work without any VAO bound, but then our VertexAttrib calls would overwrite the default one currently bound.
	GLuint vertex_array_object = 0;
#ifdef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
	glGenVertexArrays(1, &vertex_array_object);
#endif
	ImGui_ImplOpenGL3_SetupRenderState(draw_data, fb_width, fb_height, vertex_array_object);

	// Will project scissor/clipping rectangles into framebuffer space
	ImVec2 clip_off = draw_data->DisplayPos;         // (0,0) unless using multi-viewports
	ImVec2 clip_scale = draw_data->FramebufferScale; // (1,1) unless using retina display which are often (2,2)

	// Render command lists
	for (int n = 0; n < draw_data->CmdListsCount; n++)
	{
		const ImDrawList* cmd_list = draw_data->CmdLists[n];

		// Upload vertex/index buffers
		GLsizeiptr vtx_buffer_size = (GLsizeiptr)cmd_list->VtxBuffer.Size * (int)sizeof(ImDrawVert);
		GLsizeiptr idx_buffer_size = (GLsizeiptr)cmd_list->IdxBuffer.Size * (int)sizeof(ImDrawIdx);
		if (bd->VertexBufferSize < vtx_buffer_size)
		{
			bd->VertexBufferSize = vtx_buffer_size;
			glBufferData(GL_ARRAY_BUFFER, bd->VertexBufferSize, NULL, GL_STREAM_DRAW);
		}
		if (bd->IndexBufferSize < idx_buffer_size)
		{
			bd->IndexBufferSize = idx_buffer_size;
			glBufferData(GL_ELEMENT_ARRAY_BUFFER, bd->IndexBufferSize, NULL, GL_STREAM_DRAW);
		}
		glBufferSubData(GL_ARRAY_BUFFER, 0, vtx_buffer_size, (const GLvoid*)cmd_list->VtxBuffer.Data);
		glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, idx_buffer_size, (const GLvoid*)cmd_list->IdxBuffer.Data);

		for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
		{
			const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
			if (pcmd->UserCallback != NULL)
			{
				// User callback, registered via ImDrawList::AddCallback()
				// (ImDrawCallback_ResetRenderState is a special callback value used by the user to request the renderer to reset render state.)
				if (pcmd->UserCallback == ImDrawCallback_ResetRenderState)
					ImGui_ImplOpenGL3_SetupRenderState(draw_data, fb_width, fb_height, vertex_array_object);
				else
					pcmd->UserCallback(cmd_list, pcmd);
			}
			else
			{
				// Project scissor/clipping rectangles into framebuffer space
				ImVec2 clip_min((pcmd->ClipRect.x - clip_off.x) * clip_scale.x, (pcmd->ClipRect.y - clip_off.y) * clip_scale.y);
				ImVec2 clip_max((pcmd->ClipRect.z - clip_off.x) * clip_scale.x, (pcmd->ClipRect.w - clip_off.y) * clip_scale.y);
				if (clip_max.x <= clip_min.x || clip_max.y <= clip_min.y)
					continue;

				// Apply scissor/clipping rectangle (Y is inverted in OpenGL)
				glScissor((int)clip_min.x, (int)((float)fb_height - clip_max.y), (int)(clip_max.x - clip_min.x), (int)(clip_max.y - clip_min.y));

				// Bind texture, Draw
				glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->GetTexID());
#ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_VTX_OFFSET
				if (bd->GlVersion >= 320)
					glDrawElementsBaseVertex(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, (void*)(intptr_t)(pcmd->IdxOffset * sizeof(ImDrawIdx)), (GLint)pcmd->VtxOffset);
				else
#endif
					glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, (void*)(intptr_t)(pcmd->IdxOffset * sizeof(ImDrawIdx)));
			}
		}
	}

	// Destroy the temporary VAO
#ifdef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
	glDeleteVertexArrays(1, &vertex_array_object);
#endif

	// Restore modified GL state
	glUseProgram(last_program);
	glBindTexture(GL_TEXTURE_2D, last_texture);
#ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_BIND_SAMPLER
	if (bd->GlVersion >= 330)
		glBindSampler(0, last_sampler);
#endif
	glActiveTexture(last_active_texture);
#ifdef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
	glBindVertexArray(last_vertex_array_object);
#endif
	glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
	glBlendEquationSeparate(last_blend_equation_rgb, last_blend_equation_alpha);
	glBlendFuncSeparate(last_blend_src_rgb, last_blend_dst_rgb, last_blend_src_alpha, last_blend_dst_alpha);
	if (last_enable_blend) glEnable(GL_BLEND); else glDisable(GL_BLEND);
	if (last_enable_cull_face) glEnable(GL_CULL_FACE); else glDisable(GL_CULL_FACE);
	if (last_enable_depth_test) glEnable(GL_DEPTH_TEST); else glDisable(GL_DEPTH_TEST);
	if (last_enable_stencil_test) glEnable(GL_STENCIL_TEST); else glDisable(GL_STENCIL_TEST);
	if (last_enable_scissor_test) glEnable(GL_SCISSOR_TEST); else glDisable(GL_SCISSOR_TEST);
#ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_PRIMITIVE_RESTART
	if (bd->GlVersion >= 310) { if (last_enable_primitive_restart) glEnable(GL_PRIMITIVE_RESTART); else glDisable(GL_PRIMITIVE_RESTART); }
#endif

#ifdef IMGUI_IMPL_HAS_POLYGON_MODE
	glPolygonMode(GL_FRONT_AND_BACK, (GLenum)last_polygon_mode[0]);
#endif
	glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
	glScissor(last_scissor_box[0], last_scissor_box[1], (GLsizei)last_scissor_box[2], (GLsizei)last_scissor_box[3]);
	(void)bd; // Not all compilation paths use this
}

bool ImGui_ImplOpenGL3_CreateFontsTexture()
{
	ImGuiIO& io = ImGui::GetIO();
	ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();

	// Build texture atlas
	unsigned char* pixels;
	int width, height;
	io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);   // Load as RGBA 32-bit (75% of the memory is wasted, but default font is so small) because it is more likely to be compatible with user's existing shaders. If your ImTextureId represent a higher-level concept than just a GL texture id, consider calling GetTexDataAsAlpha8() instead to save on GPU memory.

	// Upload texture to graphics system
	GLint last_texture;
	glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
	glGenTextures(1, &bd->FontTexture);
	glBindTexture(GL_TEXTURE_2D, bd->FontTexture);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
#ifdef GL_UNPACK_ROW_LENGTH // Not on WebGL/ES
	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
#endif
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

	// Store our identifier
	io.Fonts->SetTexID((ImTextureID)(intptr_t)bd->FontTexture);

	// Restore state
	glBindTexture(GL_TEXTURE_2D, last_texture);

	return true;
}

void ImGui_ImplOpenGL3_DestroyFontsTexture()
{
	ImGuiIO& io = ImGui::GetIO();
	ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();
	if (bd->FontTexture)
	{
		glDeleteTextures(1, &bd->FontTexture);
		io.Fonts->SetTexID(0);
		bd->FontTexture = 0;
	}
}

// If you get an error please report on github. You may try different GL context version or GLSL version. See GL<>GLSL version table at the top of this file.
static bool CheckShader(GLuint handle, const char* desc)
{
	ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();
	GLint status = 0, log_length = 0;
	glGetShaderiv(handle, GL_COMPILE_STATUS, &status);
	glGetShaderiv(handle, GL_INFO_LOG_LENGTH, &log_length);
	if ((GLboolean)status == GL_FALSE)
		fprintf(stderr, "ERROR: ImGui_ImplOpenGL3_CreateDeviceObjects: failed to compile %s! With GLSL: %s\n", desc, bd->GlslVersionString);
	if (log_length > 1)
	{
		ImVector<char> buf;
		buf.resize((int)(log_length + 1));
		glGetShaderInfoLog(handle, log_length, NULL, (GLchar*)buf.begin());
		fprintf(stderr, "%s\n", buf.begin());
	}
	return (GLboolean)status == GL_TRUE;
}

// If you get an error please report on GitHub. You may try different GL context version or GLSL version.
static bool CheckProgram(GLuint handle, const char* desc)
{
	ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();
	GLint status = 0, log_length = 0;
	glGetProgramiv(handle, GL_LINK_STATUS, &status);
	glGetProgramiv(handle, GL_INFO_LOG_LENGTH, &log_length);
	if ((GLboolean)status == GL_FALSE)
		fprintf(stderr, "ERROR: ImGui_ImplOpenGL3_CreateDeviceObjects: failed to link %s! With GLSL %s\n", desc, bd->GlslVersionString);
	if (log_length > 1)
	{
		ImVector<char> buf;
		buf.resize((int)(log_length + 1));
		glGetProgramInfoLog(handle, log_length, NULL, (GLchar*)buf.begin());
		fprintf(stderr, "%s\n", buf.begin());
	}
	return (GLboolean)status == GL_TRUE;
}

bool    ImGui_ImplOpenGL3_CreateDeviceObjects()
{
	ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();

	// Backup GL state
	GLint last_texture, last_array_buffer;
	glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
	glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
#ifdef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
	GLint last_vertex_array;
	glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
#endif

	// Parse GLSL version string
	int glsl_version = 130;
	sscanf(bd->GlslVersionString, "#version %d", &glsl_version);

	const GLchar* vertex_shader_glsl_120 =
		"uniform mat4 ProjMtx;\n"
		"attribute vec2 Position;\n"
		"attribute vec2 UV;\n"
		"attribute vec4 Color;\n"
		"varying vec2 Frag_UV;\n"
		"varying vec4 Frag_Color;\n"
		"void main()\n"
		"{\n"
		"    Frag_UV = UV;\n"
		"    Frag_Color = Color;\n"
		"    gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
		"}\n";

	const GLchar* vertex_shader_glsl_130 =
		"uniform mat4 ProjMtx;\n"
		"in vec2 Position;\n"
		"in vec2 UV;\n"
		"in vec4 Color;\n"
		"out vec2 Frag_UV;\n"
		"out vec4 Frag_Color;\n"
		"void main()\n"
		"{\n"
		"    Frag_UV = UV;\n"
		"    Frag_Color = Color;\n"
		"    gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
		"}\n";

	const GLchar* vertex_shader_glsl_300_es =
		"precision highp float;\n"
		"layout (location = 0) in vec2 Position;\n"
		"layout (location = 1) in vec2 UV;\n"
		"layout (location = 2) in vec4 Color;\n"
		"uniform mat4 ProjMtx;\n"
		"out vec2 Frag_UV;\n"
		"out vec4 Frag_Color;\n"
		"void main()\n"
		"{\n"
		"    Frag_UV = UV;\n"
		"    Frag_Color = Color;\n"
		"    gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
		"}\n";

	const GLchar* vertex_shader_glsl_410_core =
		"layout (location = 0) in vec2 Position;\n"
		"layout (location = 1) in vec2 UV;\n"
		"layout (location = 2) in vec4 Color;\n"
		"uniform mat4 ProjMtx;\n"
		"out vec2 Frag_UV;\n"
		"out vec4 Frag_Color;\n"
		"void main()\n"
		"{\n"
		"    Frag_UV = UV;\n"
		"    Frag_Color = Color;\n"
		"    gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
		"}\n";

	const GLchar* fragment_shader_glsl_120 =
		"#ifdef GL_ES\n"
		"    precision mediump float;\n"
		"#endif\n"
		"uniform sampler2D Texture;\n"
		"varying vec2 Frag_UV;\n"
		"varying vec4 Frag_Color;\n"
		"void main()\n"
		"{\n"
		"    gl_FragColor = Frag_Color * texture2D(Texture, Frag_UV.st);\n"
		"}\n";

	const GLchar* fragment_shader_glsl_130 =
		"uniform sampler2D Texture;\n"
		"in vec2 Frag_UV;\n"
		"in vec4 Frag_Color;\n"
		"out vec4 Out_Color;\n"
		"void main()\n"
		"{\n"
		"    Out_Color = Frag_Color * texture(Texture, Frag_UV.st);\n"
		"}\n";

	const GLchar* fragment_shader_glsl_300_es =
		"precision mediump float;\n"
		"uniform sampler2D Texture;\n"
		"in vec2 Frag_UV;\n"
		"in vec4 Frag_Color;\n"
		"layout (location = 0) out vec4 Out_Color;\n"
		"void main()\n"
		"{\n"
		"    Out_Color = Frag_Color * texture(Texture, Frag_UV.st);\n"
		"}\n";

	const GLchar* fragment_shader_glsl_410_core =
		"in vec2 Frag_UV;\n"
		"in vec4 Frag_Color;\n"
		"uniform sampler2D Texture;\n"
		"layout (location = 0) out vec4 Out_Color;\n"
		"void main()\n"
		"{\n"
		"    Out_Color = Frag_Color * texture(Texture, Frag_UV.st);\n"
		"}\n";

	// Select shaders matching our GLSL versions
	const GLchar* vertex_shader = NULL;
	const GLchar* fragment_shader = NULL;
	if (glsl_version < 130)
	{
		vertex_shader = vertex_shader_glsl_120;
		fragment_shader = fragment_shader_glsl_120;
	}
	else if (glsl_version >= 410)
	{
		vertex_shader = vertex_shader_glsl_410_core;
		fragment_shader = fragment_shader_glsl_410_core;
	}
	else if (glsl_version == 300)
	{
		vertex_shader = vertex_shader_glsl_300_es;
		fragment_shader = fragment_shader_glsl_300_es;
	}
	else
	{
		vertex_shader = vertex_shader_glsl_130;
		fragment_shader = fragment_shader_glsl_130;
	}

	// Create shaders
	const GLchar* vertex_shader_with_version[2] = { bd->GlslVersionString, vertex_shader };
	GLuint vert_handle = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vert_handle, 2, vertex_shader_with_version, NULL);
	glCompileShader(vert_handle);
	CheckShader(vert_handle, "vertex shader");

	const GLchar* fragment_shader_with_version[2] = { bd->GlslVersionString, fragment_shader };
	GLuint frag_handle = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(frag_handle, 2, fragment_shader_with_version, NULL);
	glCompileShader(frag_handle);
	CheckShader(frag_handle, "fragment shader");

	// Link
	bd->ShaderHandle = glCreateProgram();
	glAttachShader(bd->ShaderHandle, vert_handle);
	glAttachShader(bd->ShaderHandle, frag_handle);
	glLinkProgram(bd->ShaderHandle);
	CheckProgram(bd->ShaderHandle, "shader program");

	glDetachShader(bd->ShaderHandle, vert_handle);
	glDetachShader(bd->ShaderHandle, frag_handle);
	glDeleteShader(vert_handle);
	glDeleteShader(frag_handle);

	bd->AttribLocationTex = glGetUniformLocation(bd->ShaderHandle, "Texture");
	bd->AttribLocationProjMtx = glGetUniformLocation(bd->ShaderHandle, "ProjMtx");
	bd->AttribLocationVtxPos = (GLuint)glGetAttribLocation(bd->ShaderHandle, "Position");
	bd->AttribLocationVtxUV = (GLuint)glGetAttribLocation(bd->ShaderHandle, "UV");
	bd->AttribLocationVtxColor = (GLuint)glGetAttribLocation(bd->ShaderHandle, "Color");

	// Create buffers
	glGenBuffers(1, &bd->VboHandle);
	glGenBuffers(1, &bd->ElementsHandle);

	ImGui_ImplOpenGL3_CreateFontsTexture();

	// Restore modified GL state
	glBindTexture(GL_TEXTURE_2D, last_texture);
	glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
#ifdef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
	glBindVertexArray(last_vertex_array);
#endif

	return true;
}

void    ImGui_ImplOpenGL3_DestroyDeviceObjects()
{
	ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();
	if (bd->VboHandle) { glDeleteBuffers(1, &bd->VboHandle); bd->VboHandle = 0; }
	if (bd->ElementsHandle) { glDeleteBuffers(1, &bd->ElementsHandle); bd->ElementsHandle = 0; }
	if (bd->ShaderHandle) { glDeleteProgram(bd->ShaderHandle); bd->ShaderHandle = 0; }
	ImGui_ImplOpenGL3_DestroyFontsTexture();
}

//--------------------------------------------------------------------------------------------------------
// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
//--------------------------------------------------------------------------------------------------------

static void ImGui_ImplOpenGL3_RenderWindow(ImGuiViewport* viewport, void*)
{
	if (!(viewport->Flags & ImGuiViewportFlags_NoRendererClear))
	{
		ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
		glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
		glClear(GL_COLOR_BUFFER_BIT);
	}
	ImGui_ImplOpenGL3_RenderDrawData(viewport->DrawData);
}

static void ImGui_ImplOpenGL3_InitPlatformInterface()
{
	ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
	platform_io.Renderer_RenderWindow = ImGui_ImplOpenGL3_RenderWindow;
}

static void ImGui_ImplOpenGL3_ShutdownPlatformInterface()
{
	ImGui::DestroyPlatformWindows();
}

#if defined(__clang__)
#pragma clang diagnostic pop
#endif